Internal combustion engine systems, such as those used to provide motive power to propel a vehicle, frequently operate at high temperatures owing to high combustion temperatures in the engine. The high temperatures may cause engine combustion stability issues and/or component degradation. As such, some engine systems may be configured to increase the amount of fuel provided to the engine during high temperature conditions. Such enrichment of the air-fuel ratio may lower combustion temperatures and prevent component degradation, but doing so increases fuel consumption and may increase emissions.
One example approach for mitigating the effects of high engine/combustion temperatures without enriching the air-fuel ratio is set forth in U.S. Pat. No. 9,169,755. Therein, water may be injected into one or more deactivated cylinders to lower catalyst temperature, thus preventing excessive catalyst temperatures that may lead to catalyst degradation.
However, the inventors herein have recognized an issue with the above approach. While injecting water into one or more deactivated cylinders may help lower catalyst temperature during some conditions, injecting water into one or more deactivated cylinders may not combat high temperature exhaust during higher load conditions where all cylinders are active. Further, injecting water into deactivated cylinders fails to take advantage of the charge dilution effects or other efficiency gains that may be realized with water injection.
In one example, the issues described above may be addressed by a method for a vehicle including, responsive to a turbine temperature being greater than a threshold temperature, injecting water stored at a water reservoir to an inlet of a turbocharger turbine of a turbocharger, responsive to the turbine temperature being less than the threshold temperature and a determined efficiency gain being greater than a threshold gain, injecting water stored at the water reservoir to the inlet of the turbocharger turbine, and responsive to the turbine temperature being less than the threshold temperature and the determined efficiency gain being less than the threshold gain, blocking injection of water stored at the water reservoir to the inlet of the turbocharger turbine. In this way, water may be injected at a turbine inlet in order to lower turbine temperatures, thus avoiding potential turbine degradation that may occur in response to prolonged exposure to high exhaust gas temperatures. Further, the water injection may be performed even when turbine temperatures are not high if an efficiency gain of the turbine that would be exhibited if the water is injected is higher than a threshold. The efficiency gain may include an increase in turbine speed caused by an increase in gas volume acting on the turbine due to the injection and subsequent vaporization of the water. By doing so, turbine degradation may be avoided without enriching air-fuel ratio during virtually any engine operating condition, and while increasing turbine efficiency during at least some conditions.
In another example, a method for a vehicle includes injecting water stored at a water reservoir into one or more of an engine cylinder, an exhaust manifold, and a turbocharger turbine inlet via one or more water injectors of a water injection system based on engine operating conditions. The method further includes, responsive to a first condition, selectively supplying water stored at the water reservoir to one or more of a windshield wiper system, engine coolant system, and drinking water system based on respective water levels in the windshield wiper system, engine coolant system, and drinking water system, and responsive to a second condition, blocking the supply of water stored at the water reservoir to the one or more of the windshield wiper system, engine coolant system, and drinking water system regardless of the respective water levels in the windshield wiper system, engine coolant system, and drinking water system.
In this way, the water reservoir may be used to supply water to one or more water injectors based on operating conditions, and the water reservoir may also be used to supply water to other water-consuming devices of the vehicle. In order to ensure water is available when water injection is commanded, thus preventing unnecessary enrichment that may waste fuel, the supply of water from the reservoir to the other water-consuming devices may be blocked during some conditions, such as when the water level in the water reservoir is low. By doing so, water injection may be used at various places in the engine system to lower gas temperatures and increase engine efficiency, and water may be supplied to auxiliary water-consuming systems, all from a single reservoir, thus simplifying packaging of the water supply to the water-consuming devices and lowering costs.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.